Do you mean 'deep' (ie, the thickness of the wall?). Is the door 6" thick or just the jamb? If just the jamb, it's probably easier to trim that rather than make your entire wall thicker.
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DA01Oct 2 '12 at 6:04

3 Answers
3

I'd suggest checking the wall for plum. You may not want the door jamb perfectly straight. If the wall tilts in or out, you can easily fix that when cutting the jamb, or have a difficult time installing the trim.
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BMitch♦Oct 2 '12 at 11:48

@BMitch - Careful there, you're describing the back garage door and the kitchen door into the garage here. A future project is getting the materials and working up the desire to run a plane to create long, tapered trim strips so I can finish out the door moldings. The garage door has an external steel security screen door and what we had to go through to remount it because the casement protrudes one inch further out at the top than the bottom was a tribute to skill with a hand plane. And the lean in both walls is a tribute to '70s style "Hick Built" ranch style homes...
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Fiasco LabsDec 1 '12 at 15:49

It is near impossible to answer your question effectively without more details. It is always possible to build out the wall to fit the door. The difficulty here is knowing where exactly your problem is. I want to suggest you think of the door as an architectural feature of the wall. It does not need to be the same thickness because it is providing an opportunity for variation and emphasis. This would be accomplished by positioning the gate in the opening of the wall (this might start as a mental exercise) next imagine making a transition from the fence to the frame of the gate by adding new material at the gap between fence and frame. Usually a few sticks of various sizes can be used to create a pleasing transition from one to the other. Look at how door frames are transitioned to the surrounding wall with moldings. In your case the "moldings" would be larger sticks, perhaps one or two pieces on each side. These pieces can also function to attach the frame to the fence or they can hide the cruder work done to attach the frame of the gate firmly to the fence. Please ask questions for clarification.

Think of the door as something in the middle of a picture frame. Add layers of " mat, in this case 1 by material or more likely 5/4 material in concentric layers with pleasing reveals to shim out that section of wall with the last layer overlapping the jamb to a 1/4 inch reveal. The hard part without a surface planer will be to calculate how many and which layers to use where to make up the difference in an aesthetically pleasing manner.

Alternatively trimming the jambs to fit the wall thickness would work, but is not especially easy if you want to keep the frame of the pre-hung door together.